The present application relates to estimating a channel in an apparatus for receiving an orthogonal frequency division multiplexing (OFDM) signal.
Digital high definition television (HDTV) broadcasting systems compress digital data of about 1 gigabits per second (Gbps) obtained from various HD image sources into data of 15˜18 Megabits per second (Mbps) and transmit the digital data of several Mbps using a limited bandwidth channel of 6˜8 megahertz (MHz). Because the HDTV broadcasting systems also transmit digital data of several tens of Mbps using the limited bandwidth channel of 6˜8 MHz, high bandwidth efficiency is needed. Also, HDTV broadcasting systems adopt a terrestrial simultaneous broadcasting method that uses a very high frequency/ultra high frequency (VHF/UHF) channel allocated for conventional analog TV broadcasting and thus have to overcome interference on the same channel by an analog TV channel.
To increase transmission efficiency of each bandwidth and prevent interference, orthogonal frequency division multiplexing (OFDM) is selected as next generation HDTV terrestrial broadcasting from among a variety of possible digital modulations. OFDM converts a symbol sequence in serial form to symbols in parallel formed in a block unit, and multiplexes the parallel symbols at different subcarrier frequencies.
OFDM uses multiple closely-spaced orthogonal subcarriers to carry data. If a multiplication of two carriers results in 0, both carriers are orthogonal to each other. Orthogonal carrier waves are used to increase spectrum efficiency by overlapping carrier spectrums. To extract digital data from an OFDM modulated signal, receivers can estimate a channel.